560 DOROUCOULIS CHAP. that of Mycetes. Nevertheless Professor "Weldon1 has found in a female of C. gigot a patch of ossification on the thyroid cartilage of the larynx which may be an indication of something more in the male. There are eleven species. NyctipitKecus, the Doroucouli Monkeys, is a genus of some- what Lemuriiie appearance, caused by their large eyes. But they reminded Bates of an Owl or a Tiger-cat! They have a long, but not prehensile tail. As in the Marmosets, the lower incisors project forwards in a Lemurine fashion. The thumb is very short. A peculiarity of this genus is the twenty-two dorso- lumbar vertebrae. As in Chrysothrix, but not as in Callithrix, the hemispheres of the brain are smooth. There are five species, of which one occurs so far north as Nicaragua; the rest are Brazilian, extending down to the Argentine. The Ouakari Monkeys, BrcwTiyurus? are, as the name denotes, short-tailed forms. Two species, B. rubicundus and B. calvus, Fia. 266.óRed-faced Onakari. Braahyurua r*itncund<u$. x £. have bright red faces; JR. melanoc&pTicd-us has a black one. There is a small thumb. The brain is fairly convoluted, and is to be specially compared with that of Cebv* and Pifliccia. The 1 "Hotes on Cattithrix gigot," Proc. Zool. Soc. 1884, p. 6. a Forbes, Proc. Zool. &oc. 188O, p. 639.